1. Field of the Invention
This invention relates to an electronic musical instrument to an (EMI), especially EMI provided with a limited number of tone generators (called a key assigner system) which generates tone signals of various feet. In the EMI, there are tone signals such as 16', 8', 4' (defined here as octave series), and tone signals such as 51/3', 22/3' (defined as non-octave series in this description).
2. Description of the Prior Art
The tone signals generated in the non-octave series, for instance 51/3', is 7 semi-tones higher than the tone signal of 8'. In other words, the tone signal generated as 51/3' when the key for note C is pressed, has the same frequency of the tone signal generated in 8' when the key for note G is pressed. To generate the non-octave series tone signals in a usual EMI with the key assigner system, for example, to generate the quint series tone signal such as 51/3' or 22/3', it is necessary to obtain the highest signal which has a frequency 3 times higher than the highest pitch signal necessary in usual octave series tone generators. There then must be a divider to divide such a signal by 2 to supply the non-octave series tone generator (TG), and another divider to divide the signal by 3 to supply the octave series TG. A binary counter in each TG then divides the highest pitch signal supplied to each TG to obtain the tone signals.
Therefore, there is a problem with respect to the tone signals generated by the system described above: such signals are pure temperament and not temperament (the standard) and the frequency is different between temperament and pure temperament. Moreover, because the frequency of the highest pitch signal is 3 times higher than usual, it is necessary to use high speed devices.
On the other hand, printed circuit boards are often shared. FIG. 1 shows the usual EMI using the key assigner system. Referring to FIG. 1, element 1 is the keyboards. Element 2 is a generator assigner (GA). GA 2 detects the key stroke and selects a TG not being used out of several TGs then, GA 2 supplies the assignment signals which consist of (1) note data which represents the note name of the tone signal to be generated by the TG, (2) octave data which represents the octave number of the tone signal to be generated by the TG, and (3) a key-on signal which indicates that the key is being pressed. GA 2 may be a circuit which has the same function described in Japanese Patent Publication No. 50-33407/1975 which corresponds to U.S. Pat. No. 3,610,799. Element 3 is a top octave synthesizer (TOS) which generates the 12 highest pitch signals corresponding to each note (C, C.music-sharp., - - - , B). Element 4-1 through 4-n are tone generators which generate tone signals according to the assignment signals supplied by the GA 2. Element 5 is a note selector and is controlled by note data supplied by GA 2 so as to select one highest pitch signal out of the 12 highest pitch signals supplied by TOS 3. Element 6 is a binary counter. Binary counter 6 consists of 7 stages of toggle flip flops, and is arranged so as to divide the highest pitch signal (applied by a note selector 5) into 7 pitch signals. The frequency of the outputs from terminal Q0 through Q6 follows the equation below: EQU (output from Qn)=2.multidot.(output from Qn+1) (1)
where 0.ltoreq.n.ltoreq.5.
Element 7-1 through 7-4 are octave selectors which select one pitch signal out of 7 pitch signals supplied by the binary counter 6. The octave data is applied to the octave selectors 7-1 through 7-4 as the control input. Element 8-1 through 8-4 are keyers which control the amplitude of the pitch signals supplied by the octave selectors 7-1 through 7-4. The busbar selectors 9-1, 9-2, and 9-3 distribute the pitch signals applied by the keyers 8-2 through 8-4 to the output terminals specified by the assignment signals (octave data). Tone color filters are connected to each output terminal.
The operation of the circuit shown in FIG. 1 is as follows:
When a key is pressed, GA 2 supplies the assignment signal to the TG which is not otherwise being used. Every key is determined by note name and octave number. In this embodiment, GA 2 supplies note data, octave data and key-on signal. The note data consists of a 4 bit digital signal N0, N1, N2, N3 as shown in Table 1. The octave data consists of a 2 bit digital signal O1, O2 as shown in Table 2. The key-on signal indicates that the key is being pressed.
On the other hand, when TG 4-1 receives the assignment signals, at first, the note selector 5 selects one highest pitch signal out of the 12 highest pitch signals supplied by TOS 3 according to the note data N3 through N0. The binary counter 6 divides the highest pitch signal selected by note selector 5 and outputs 7 pitch signals from output terminals Q0 through Q6. The octave selectors 7-1 through 7-4 determine the range of pitch signals in response to the octave data O2 and O1 supplied by GA 2. The relationship between the output signal from terminal X and octave data O2 and O1 is shown in Table 3. For example, if the octave data O2 and O1 is 01, octave selector 7-1 selects the pitch signal connected to the input terminal X1. That is, the pitch signal outputted from the output terminal Q1 of the binary counter 6 is selected.
Now, the difference in frequency between the each output of octave selectors 7-1 through 7-4 is one octave, because the same octave data O2 and O1 is applied to control the octave selectors 7-1 through 7-4, but the inputs to terminals X0 through X3 of octave selectors 7-1, 7-2, 7-3, 7-4 are one octave different from each other. This is also true for terminals X1 through X3 of the octave selectors 7-1 through 7-4. The pitch signals outputted by octave selectors 7-1 through 7-4 are modulated in amplitude by the keyers 8-1 through 8-4. The output from the keyer 8-1 is outputted from TG 4-1 as 2' tone signal. The outputs from the keyers 8-2 through 8-4 are distributed to the specified tone color filters through the busbar selectors 9-1 through 9-3 as 4', 8', 16' tone signals respectively according to the octave data applied to the busbar selectors 9-1, 9-2, and 9-3. Here, the busbar selectors 9-1 through 9-3 distribute the input signal as shown in Table 4. In other words, the busbar selectors 9-1 through 9-3 output the tone signal from terminal X0 when the octave data is 00, from terminal X1 when the octave data is 01, from terminal X2 when the octave data is 10, from terminal X3 when the octave data is 11.
If one tries to use the TG surrounded by the dotted line as the quint series TG, TG 4-1 has the following defects.
TGs 4-1 through 4-n operate correctly when both note data and octave data are as shown in Table 1 and 2 respectively. Therefore, when the C1 key is pressed, TG 4-1 operates correctly as the quint series TG if GA 2 supplies note data 1000 and octave data 00, instead of note data 0001 and octave data 00. As shown in Table 5, octave data O1, O2 is 00 for C1 through E1, but octave data must be 01 for F1 through B1. That is, octave data for the note names F through B are equal to the octave data for the note names C through E plus one, respectively. Therefore, the octave data from F4 through B4 must be a repetition of C4 through E4 for the octave data consists of 2 bit digital signals. That means the frequency of the tone signal for F4 through B4 is the same as the frequency of the tone signal for F3 through B3 respectively.
Concerning the distribution of the pitch signals outputted by the busbar selectors 9-1 through 9-3, terminal X0 outputs 5 pitch signals (C1 through E1), but the terminal X3 outputs 19 pitch signals (F3 through B3, C4 through B4). This means the tone color filter connected to the terminal X3 has to take care of 19 tone signals. Therefore, the tone color of the highest tone signal outputted by that tone color filter is different from the tone color of the lowest tone signal outputted by that tone color filter.
Because the tone color filter is selected by the octave data, it outputs the same number of tone signals if the octave data for quint series TG and the octave data for octave series TG are the same. But in that case, the TG generates a tone signal one octave lower than it is supposed to generate for the keys F through B.